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    Confused on Tx wireless protocol- Latency/eCCPM/normal

    LINK1

    Im currently finding on how the transmitter latency works.

    So firstly, Im an electronics student and know pretty much everything electrically. Regarding the topic of Wireless- Is not at all my strongest.
    Im a person who believes in Evidence. So dont tell me "Buy a Futaba/Spektrum and it'll solve all your problem".

    Following the link above, I see that the table is classified into 2.4GHz with eCCPM and at the bottom there's the PPM & normal 6 channel as well as the DSM/FHSS/ETC ETC.

    What I am confused is that:

    What are the difference between those tables?
    1)Correct me if im wrong but, eCCPM Only used on Heli?

    2)So what does a plane use? Lets say im having the standard thr,ale,ele& RUDD. And I have 50% throttle, FULL LEFT on rudd and Ale. Full up on Elev. So how does it transmitter send the signals? From what I understand, it would need to send Ch1,CH2,CH3,CH4 in order right? They can't possible send out as a whole Package Simultaneously right??

    3)I understand that Different brands uses different protocol. (Eg. Dsm/Fhss/ etc)

    If anyone could gladly guide me. It would be great! A detailed explanation would be.. VERY THANKFUL!

    Thanks in ADVANCE!!


    P.S. Im looking into buying a new radio,thus this thread. Currently looking at the Futaba SG14/Spektrum DX9

    Main Purpose/Concerns
    1) Long range ( Not a real concern as Im looking to modding the electronics inside)
    2) Low latency (Very big concern here)

    Futaba:
    + Side: Heard the FASST has pretty good long range.
    - Side: My hands are one fussy pair

    Spektrum:
    + Side: I think i had an Hand-or-gasm.
    - Side: People keep telling me about Spektrum's history (Im not good with history, so if someone could enlighten me on this, it will be great as well)

    #2
    TL;DR: Lots of conflicting information out there, but odds are your brain and CNS are slower than the frame rate and latency on these systems, so pick a radio that has a decent UI. I like the opentx-capable stuff like the Taranis or the 9XR, but the learning curve on the UI may be steep. I also recommend the Spektrum kit to new people because it more-or-less works out of the box, clone Rx are cheap, and there are several BNF models available. Just get a tx and start flying.


    Originally posted by emo_121 View Post
    What are the difference between those tables?
    1)Correct me if im wrong but, eCCPM Only used on Heli?
    Yes, that is a heli-specific mixing mode. Usually this is implemented as a channel mixer on the transmitter. It doesn't affect latency if the software continues to output frames at the same rate. There are exceptions with badly designed controllers, but I've not seen one of those for ages. All it really does is just mix the collective and cyclic terms together to make the swash move in the right manner on a heli.

    Originally posted by emo_121 View Post
    2)So what does a plane use? Lets say im having the standard thr,ale,ele& RUDD. And I have 50% throttle, FULL LEFT on rudd and Ale. Full up on Elev. So how does it transmitter send the signals? From what I understand, it would need to send Ch1,CH2,CH3,CH4 in order right? They can't possible send out as a whole Package Simultaneously right??
    A fixed wing RC aircraft would use the same framing format. I cannot speak for Futaba's FAAST, but spektrum's DSMX and DSM2 basically, after appropriate despreading, sends a 22ms or 11ms frame, containing the channel data in sequential order. Note that even 22ms is a very fast frame rate. It's going to take more than 22ms for a signal from your eyes to get to your fingers, so you are probably the weakest link in the whole system, and I'd argue that, if you consider full closed-loop operation, most modern radios are plenty low-latency. However, there might be some open-loop maneuvering that happens, and in which case your brain might detect some "lag" due to it expecting a response some time ahead. However, I've not seen a study of RC aircraft operations and what that entails.

    The reason that you might hear bad things about DSM2/DSMX is due to the fact that the DX6i and DX7 are designed to meet conservative RF emissions profiles for sale in the EU. This does mean that range suffers a bit. DSM2 also has a bug where it might select channels that are close together and suseptable to interference. As a result, frames are lost, and "lag" is experienced. With a modern DSMX setup, and if you fly within line of sight as good practice dictates, and you don't go do something utterly stupid like put a 2.4GHz transmitter right next to the receiver, you should be good.

    Comment


      #3
      Originally posted by timgoh0 View Post
      TL;DR: Lots of conflicting information out there, but odds are your brain and CNS are slower than the frame rate and latency on these systems, so pick a radio that has a decent UI. I like the opentx-capable stuff like the Taranis or the 9XR, but the learning curve on the UI may be steep. I also recommend the Spektrum kit to new people because it more-or-less works out of the box, clone Rx are cheap, and there are several BNF models available. Just get a tx and start flying.
      Yeah I have an 9XR and Spektrum DX6I currently.I prefer using the 9XR than DX6I. 9XR Software is really great and really technical, which i loved it. However, I find the latency too darn slow. Im using it with the DJT module. Paired with V8frII, TOO DAMM BLOODY SLOW). Currently paired with D6FR, Feels the improvement but still felt it very slow.



      Originally posted by timgoh0 View Post
      A fixed wing RC aircraft would use the same framing format. I cannot speak for Futaba's FAAST, but spektrum's DSMX and DSM2 basically, after appropriate despreading, sends a 22ms or 11ms frame, containing the channel data in sequential order. Note that even 22ms is a very fast frame rate. It's going to take more than 22ms for a signal from your eyes to get to your fingers, so you are probably the weakest link in the whole system, and I'd argue that, if you consider full closed-loop operation, most modern radios are plenty low-latency. However, there might be some open-loop maneuvering that happens, and in which case your brain might detect some "lag" due to it expecting a response some time ahead. However, I've not seen a study of RC aircraft operations and what that entails.
      I do not know but, I certainly feels the latency. I know it's rather hard to prove that humans cant feel that high latency like how our eyes cant see a screen higher than 60HZ refresh rate. I certainly can. I tried my hands on Futaba 10J, it felt pretty fast though, but unable to compare to my other 2 radios because they were of different platform.

      Thanks anyway!

      I wonder how futaba's FAAST works.. HMMMMM

      Comment


        #4
        Originally posted by emo_121 View Post
        Yeah I have an 9XR and Spektrum DX6I currently.I prefer using the 9XR than DX6I. 9XR Software is really great and really technical, which i loved it. However, I find the latency too darn slow. Im using it with the DJT module. Paired with V8frII, TOO DAMM BLOODY SLOW). Currently paired with D6FR, Feels the improvement but still felt it very slow.
        Are you sure there's a difference? I've measured the latency on my Taranis's native radio with the X8R ACCST receiver, and it's about 1-2ms faster than DSMX via one of those Orange modules on the same radio. It's quite likely that some of this is psychological. Perhaps some of it is a result of the 9xr's serialization latency.

        More importantly: what does the radio "lag" cause? Does the model become uncontrollable?




        Originally posted by emo_121 View Post
        I do not know but, I certainly feels the latency. I know it's rather hard to prove that humans cant feel that high latency like how our eyes cant see a screen higher than 60HZ refresh rate. I certainly can. I tried my hands on Futaba 10J, it felt pretty fast though, but unable to compare to my other 2 radios because they were of different platform.

        Thanks anyway!

        I wonder how futaba's FAAST works.. HMMMMM
        FAAST appears to be a frequency hopping spread spectrum protocol, but there are very little details about the exact implementation.

        Comment


          #5
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          Comment


            #6
            Originally posted by timgoh0 View Post
            Are you sure there's a difference? I've measured the latency on my Taranis's native radio with the X8R ACCST receiver, and it's about 1-2ms faster than DSMX via one of those Orange modules on the same radio. It's quite likely that some of this is psychological. Perhaps some of it is a result of the 9xr's serialization latency.
            I think it got to do with the X8r receiver. One day i shall take a chance and try out the x8r Receiver. Are you using the DJT or the XJT module? I think there will be difference in latency as well.

            Comment


              #7
              Originally posted by emo_121 View Post
              I think it got to do with the X8r receiver. One day i shall take a chance and try out the x8r Receiver. Are you using the DJT or the XJT module? I think there will be difference in latency as well.
              I'm using the on-board XJT module. I have a x8r rx if you want to borrow it for a few hours and bring your radio along to test it. However, I highly doubt that any latency measureable will result in a visible difference.

              I wonder if people know of any minimum latency threshold study for RC operations.

              Comment


                #8
                Just adding info to this old thread as I own an JR.

                According to JR ( not me ), with the DMSS technology on the XG series transmitter, when you select CCPM mixing, all three channels ( chn 2, 3 ,6 ) of the swash plate will send out the signals at the same time, meaning there is no lag or latency to the swash.

                You can see the info-picture here from JR Propo.



                Although I cant feel the difference but what the hell, its japan and I like JDM LOLX
                I'm Remotely Controlled ...

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